A concept I rarely see explored to its full, chilling potential is the house that isn't haunted by a ghost, but by a living person’s consciousness—someone in a coma, perhaps, whose psychic distress warps the location. The scares wouldn’t come from jump-scares, but from a slow, inescapable merging of realities. The protagonist starts finding their own memories replaced by the coma patient’s traumatic ones, or the house’s layout shifts to match the neural pathways of a damaged brain.
This setup moves beyond typical ghost lore into a psychological and almost cosmic horror space. It asks if a ‘haunting’ requires death, or if extreme, trapped consciousness is enough. The house becomes a prison for two minds, and the haunting is a desperate, invasive attempt at communication or escape. The climax wouldn’t be an exorcism, but a terrible choice: sever the link and essentially kill the trapped person, or allow the fusion to continue. That moral horror, baked into the architectural horror, lingers far longer than a slamming door.
You could layer in found documents—medical charts, frantic diary entries from before the incident—that aren’t about ghosts, but about a medical mystery, making the supernatural feel grounded in a terrifying scientific possibility.